Small intestinal permeability. Small intestinal permeability was assessed
on day 28 before weighing by using the lactulose to mannitol
differential absorption test (21). Briefly, urine samples of piglets per
treatment (n = 6) were collected after 6 h of feed deprivation for baseline
urinary sugar measurement. After the samples were obtained, 5 mL lactulose
(0.4 g/mL; Sigma) and 5 mL of mannitol (0.2 g/L; Sigma) were
administered intragastrically to the piglets. Piglets were feed-deprived for
the 6-h study period but were allowed to drink water after 30 min. Urinary
lactulose and mannitol concentrations were determined by an enzymatic
technique (22). Mannitol excretion was corrected by subtraction of baseline
values, and the lactulose to mannitol excretion ratio was calculated as an
index of intestinal permeability.